How to check port occupancy in Linux

Linux method to check port occupancy: 1. Use the lsof command, the syntax format is "lsof -i: port number"; 2. Use the netstat command, which can display the ports and processes of tcp and udp, etc. In this case, the syntax format is "netstat -tunlp | grep port number".

#The operating environment of this tutorial: Red Hat Enterprise Linux 6.1 system, Dell G3 computer.

Linux can use the lsof and netstat commands to check the port occupancy.

lsof

lsof (list open files) is a tool that lists open files on the current system.

lsof Check the port occupancy Syntax format:

lsof -i:端口号

Example

Check the server 8000 port occupancy:

# lsof -i:8000
COMMAND   PID USER   FD   TYPE   DEVICE SIZE/OFF NODE NAME
nodejs  26993 root   10u  IPv4 37999514      0t0  TCP *:8000 (LISTEN)

You can see Port 8000 is already occupied by the light nodejs service.

lsof -i requires root user permissions to execute, as shown below:

More lsof commands are as follows ：

lsof -i:8080：查看8080端口占用
lsof abc.txt：显示开启文件abc.txt的进程
lsof -c abc：显示abc进程现在打开的文件
lsof -c -p 1234：列出进程号为1234的进程所打开的文件
lsof -g gid：显示归属gid的进程情况
lsof +d /usr/local/：显示目录下被进程开启的文件
lsof +D /usr/local/：同上，但是会搜索目录下的目录，时间较长
lsof -d 4：显示使用fd为4的进程
lsof -i -U：显示所有打开的端口和UNIX domain文件

netstat

netstat -tunlp is used to display tcp, udp ports and processes and other related situations.

netstat View port occupancy Syntax format:

netstat -tunlp | grep 端口号

• -t (tcp) Only display tcp related options

• -u (udp) Only display udp related options

• -n Refuse to display aliases, convert all numbers that can be displayed into numbers

• -l List only Out of the service status of Listen (monitoring)

• -p Display the name of the program that establishes the relevant link

For example, to view the situation of port 8000, use The following commands:

# netstat -tunlp | grep 8000
tcp        0      0 0.0.0.0:8000            0.0.0.0:*               LISTEN      26993/nodejs

More commands:

netstat -ntlp   //查看当前所有tcp端口
netstat -ntulp | grep 80   //查看所有80端口使用情况
netstat -ntulp | grep 3306   //查看所有3306端口使用情况

Related recommendations: "Linux Video Tutorial"

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